overriding a tuple's __init__

Michele Simionato mis6 at pitt.edu
Mon Aug 18 23:43:06 CEST 2003


"Andrew Dalke" <adalke at mindspring.com> wrote in message news:<bhq648$s4t$1 at slb3.atl.mindspring.net>...
> Simon Burton:
> > >>> class pair(tuple):
> > ...   def __init__(self,a,b):
> > ...     tuple.__init__(self, (a,b) )
>  
> > What gives? (yes it works with a list, but i need immutable/hashable)
> 
> The problem is the immutability.  This one one of the
> new changes in 2.3 

<nitpick mode> Actually this was a change in 2.2 </nitpick mode>

__new__ is needed to acts on the creation of immutable objects and this 
is the right way to use it; unfortunaly it gives room to plenty of abuses:

class YouThinkIamAString(str):
    def __new__(cls,arg):
        return 42

print YouThinkIamAString("What's the answer?")

Yes, in Python you cannot modify the builtins, but still you have plenty
of rope to shoot in your foot ;)



                                         Michele




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